draft-ietf-dnsop-onion-tld-00.txt   draft-ietf-dnsop-onion-tld-01.txt 
dnsop J. Appelbaum dnsop J. Appelbaum
Internet-Draft The Tor Project, Inc Internet-Draft The Tor Project, Inc
Intended status: Standards Track A. Muffett Intended status: Standards Track A. Muffett
Expires: December 21, 2015 Facebook Expires: March 12, 2016 Facebook
June 19, 2015 September 9, 2015
The .onion Special-Use Domain Name The .onion Special-Use Domain Name
draft-ietf-dnsop-onion-tld-00 draft-ietf-dnsop-onion-tld-01
Abstract Abstract
This document registers the ".onion" Special-Use Domain Name. This document registers the ".onion" Special-Use Domain Name.
Status of This Memo Status of This Memo
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provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on December 21, 2015. This Internet-Draft will expire on March 12, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 2 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. The ".onion" Special-Use Domain Name . . . . . . . . . . . . 2 2. The ".onion" Special-Use Domain Name . . . . . . . . . . . . 3
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . 5 5.1. Normative References . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . 5 5.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
The Tor network [Dingledine2004] has the ability to host network The Tor network [Dingledine2004] has the ability to host network
services using the ".onion" Special-Use Top-Level Domain. Such services using the ".onion" Special-Use Top-Level Domain. Such names
addresses can be used as other domain names would be (e.g., in URLs can be used as other domain names would be (e.g., in URLs [RFC3986]),
[RFC3986]), but instead of using the DNS infrastructure, .onion names but instead of using the DNS infrastructure, .onion names
functionally correspond to the identity of a given service, thereby functionally correspond to the identity of a given service, thereby
combining location and authentication. combining location and authentication.
.onion names are used to provide access to end to end encrypted,
secure, anonymized services; that is, the identity and location of
the server is obscured from the client. The location of the client
is obscured from the server. The identity of the client may or may
not be disclosed through an optional cryptographic authentication
process.
.onion names are self-authenticating, in that they are derived from
the cryptographic keys used by the server in a client-verifiable
manner during connection establishment. As a result, the
cryptographic label component of a .onion name is not intended to be
human-meaningful.
The Tor network is designed to not be subject to any central
controlling authorities with regards to routing and service
publication, so .onion names cannot be registered, assigned,
transferred or revoked. "Ownership" of a .onion name is derived
solely from control of a public/private key pair which corresponds to
the algorithmic derivation of the name.
In this way, .onion names are "special" in the sense defined by In this way, .onion names are "special" in the sense defined by
[RFC6761] Section 3; they require hardware and software [RFC6761] Section 3; they require hardware and software
implementations to change their handling, in order to achieve the implementations to change their handling in order to achieve the
desired properties of the name (see Section 4). These differences desired properties of the name (see Section 4). These differences
are listed in Section 2. are listed in Section 2.
Like Top-Level Domain Names, .onion addresses can have an arbitrary Like Top-Level Domain Names, .onion names can have an arbitrary
number of subdomain components. This information is not meaningful number of subdomain components. This information is not meaningful
to the Tor protocol, but can be used in application protocols like to the Tor protocol, but can be used in application protocols like
HTTP [RFC7230]. HTTP [RFC7230].
Note that .onion names are required conform to DNS name syntax (as
defined in Section 3.5 of [RFC1034] and Section 2.1 of [RFC1123]), as
they will still be exposed to DNS implementations.
See [tor-address] and [tor-rendezvous] for the details of the See [tor-address] and [tor-rendezvous] for the details of the
creation and use of .onion names. creation and use of .onion names.
1.1. Notational Conventions 1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. The ".onion" Special-Use Domain Name 2. The ".onion" Special-Use Domain Name
These properties have the following effects upon parties using or These properties have the following effects upon parties using or
processing .onion names (as per [RFC6761]): processing .onion names (as per [RFC6761]):
1. Users: human users are expected to recognize .onion names as 1. Users: Human users are expected to recognize .onion names as
having different security properties, and also being only having different security properties (see Section 1), and also as
available through software that is aware of onion addresses. being only available through software that is aware of onion
names.
2. Application Software: Applications (including proxies) that 2. Application Software: Applications (including proxies) that
implement the Tor protocol MUST recognize .onion names as special implement the Tor protocol MUST recognize .onion names as special
by either accessing them directly, or using a proxy (e.g., SOCKS by either accessing them directly, or using a proxy (e.g., SOCKS
[RFC1928]) to do so. Applications that do not implement the Tor [RFC1928]) to do so. Applications that do not implement the Tor
protocol SHOULD generate an error upon the use of .onion, and protocol SHOULD generate an error upon the use of .onion, and
SHOULD NOT perform a DNS lookup. SHOULD NOT perform a DNS lookup.
3. Name Resolution APIs and Libraries: Resolvers MUST either either 3. Name Resolution APIs and Libraries: Resolvers MUST either respond
respond to requests for .onion names by resolving them according to requests for .onion names by resolving them according to
to [tor-rendezvous] or by responding with NXDOMAIN. [tor-rendezvous] or by responding with NXDOMAIN.
4. Caching DNS Servers: Caching servers SHOULD NOT attempt to look 4. Caching DNS Servers: Caching servers, where not explicitly
up records for .onion names. They MUST generate NXDOMAIN for all adapted to interoperate with Tor, SHOULD NOT attempt to look up
records for .onion names. They MUST generate NXDOMAIN for all
such queries. such queries.
5. Authoritative DNS Servers: Authoritative servers MUST respond to 5. Authoritative DNS Servers: Authoritative servers MUST respond to
queries for .onion with NXDOMAIN. queries for .onion with NXDOMAIN.
6. DNS Server Operators: Operators MUST NOT configure an 6. DNS Server Operators: Operators MUST NOT configure an
authoritative DNS server to answer queries for .onion. If they authoritative DNS server to answer queries for .onion. If they
do so, client software is likely to ignore any results (see do so, client software is likely to ignore any results (see
above). above).
7. DNS Registries/Registrars: Registrars MUST NOT register .onion 7. DNS Registries/Registrars: Registrars MUST NOT register .onion
names; all such requests MUST be denied. names; all such requests MUST be denied.
Note that the restriction upon the registration of .onion names does
not prohibit IANA from inserting a record into the root zone database
to reserve the name.
Likewise, it does not prevent non-DNS service providers (such as
trust providers) from supporting .onion names in their applications.
3. IANA Considerations 3. IANA Considerations
This document registers "onion" in the registry of Special-Use Domain This document registers "onion" in the registry of Special-Use Domain
Names [RFC6761]. See Section 2 for the registration template. Names [RFC6761]. See Section 2 for the registration template.
4. Security Considerations 4. Security Considerations
.onion names are often used to provide access to end to end The security properties of .onion names can be compromised if, for
encrypted, secure, anonymized services; that is, the identity and example:
location of the server is obscured from the client. The location of
the client is obscured from the server. The identity of the client
may or may not be disclosed through an optional cryptographic
authentication process.
These properties can be compromised if, for example:
o The server "leaks" its identity in another way (e.g., in an o The server "leaks" its identity in another way (e.g., in an
application-level message), or application-level message), or
o The access protocol is implemented or deployed incorrectly, or o The access protocol is implemented or deployed incorrectly, or
o The access protocol itself is found to have a flaw. o The access protocol itself is found to have a flaw.
.onion names are self-authenticating, in that they are derived from
the cryptographic keys used by the server in a client verifiable
manner during connection establishment. As a result, the
cryptographic label component of a .onion name is not intended to be
human-meaningful.
The Tor network is designed to not be subject to any central
controlling authorities with regards to routing and service
publication, so .onion names cannot be registered, assigned,
transferred or revoked. "Ownership" of a .onion name is derived
solely from control of a public/private key pair which corresponds to
the algorithmic derivation of the name.
Users must take special precautions to ensure that the .onion name Users must take special precautions to ensure that the .onion name
they are communicating with is correct, as attackers may be able to they are communicating with is the intended one, as attackers may be
find keys which produce service names that are visually or able to find keys which produce service names that are visually or
semantically similar to the desired service. semantically similar to the desired service. This risk is magnified
because .onion names are typically not human-meaningful. It can be
mitigated by generating human meaningful .onion names (at
considerable computing expense), or through users using bookmarks and
other trusted stores when following links.
Also, users need to understand the difference between a .onion name Also, users need to understand the difference between a .onion name
used and accessed directly via Tor-capable software, versus .onion used and accessed directly via Tor-capable software, versus .onion
subdomains of other top-level domain names and providers (e.g., the subdomains of other top-level domain names and providers (e.g., the
difference between example.onion and example.onion.tld). difference between example.onion and example.onion.tld).
The cryptographic label for a .onion name is constructed by applying The cryptographic label for a .onion name is constructed by applying
a function to the public key of the server, the output of which is a function to the public key of the server, the output of which is
rendered as a string and concatenated with the string ".onion". rendered as a string and concatenated with the string ".onion".
Dependent upon the specifics of the function used, an attacker may be Dependent upon the specifics of the function used, an attacker may be
able to find a key that produces a collision with the same .onion able to find a key that produces a collision with the same .onion
name with substantially less work than a cryptographic attack on the name with substantially less work than a cryptographic attack on the
full strength key. If this is possible the attacker may be able to full strength key. If this is possible the attacker may be able to
impersonate the service on the network. impersonate the service on the network.
If client software attempts to resolve a .onion name, it can leak the A legacy client may inadvertently attempt to resolve a ".onion" name
identity of the service that the user is attempting to access to DNS through the DNS. This causes a disclosure that the client is
resolvers, authoritative DNS servers, and observers on the attempting to use Tor to reach a specific service. Malicious
intervening network. This can be mitigated by following the resolvers could be engineered to capture and record such leaks, which
recommendations in Section 2. might have very adverse consequences for the well-being of the Tor
user. This issue is mitigated if the client's Tor software is
updated to not leak such queries, or if the client's DNS software is
updated to drop any request to the ".onion" TLD.
5. References 5. References
5.1. Normative References 5.1. Normative References
[Dingledine2004]
Dingledine, R., Mathewson, N., and P. Syverson, "Tor: the
second-generation onion router", 2004,
<https://spec.torproject.org/tor-spec>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names", [RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
RFC 6761, February 2013. RFC 6761, DOI 10.17487/RFC6761, February 2013,
<http://www.rfc-editor.org/info/rfc6761>.
[tor-address]
Mathewson, N. and R. Dingledine, "Special Hostnames in
Tor", September 2001, <https://spec.torproject.org/
address-spec>.
[tor-rendezvous]
Mathewson, N. and R. Dingledine, "Tor Rendezvous
Specification", April 2014, <https://spec.torproject.org/
rend-spec>.
5.2. Informative References 5.2. Informative References
[Dingledine2004] [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
Dingledine, R., Mathewson, N., and P. Syverson, "Tor: the STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
second-generation onion router", 2004, <https://www.onion- <http://www.rfc-editor.org/info/rfc1034>.
router.net/Publications/tor-design.pdf>.
[RFC1123] Braden, R., Ed., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, DOI 10.17487/
RFC1123, October 1989,
<http://www.rfc-editor.org/info/rfc1123>.
[RFC1928] Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and [RFC1928] Leech, M., Ganis, M., Lee, Y., Kuris, R., Koblas, D., and
L. Jones, "SOCKS Protocol Version 5", RFC 1928, March L. Jones, "SOCKS Protocol Version 5", RFC 1928, DOI
1996. 10.17487/RFC1928, March 1996,
<http://www.rfc-editor.org/info/rfc1928>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005. 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June
2014.
[tor-address]
Mathewson, N. and R. Dingledine, "Special Hostnames in
Tor", September 2001,
<https://gitweb.torproject.org/torspec.git/plain/address-
spec.txt>.
[tor-rendezvous] [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Mathewson, N. and R. Dingledine, "Tor Rendezvous Protocol (HTTP/1.1): Message Syntax and Routing", RFC
Specification", April 2014, 7230, DOI 10.17487/RFC7230, June 2014,
<https://gitweb.torproject.org/torspec.git/plain/rend- <http://www.rfc-editor.org/info/rfc7230>.
spec.txt>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Thanks to Roger Dingledine, Linus Nordberg, and Seth David Schoen for Thanks to Roger Dingledine, Linus Nordberg, and Seth David Schoen for
their input and review. their input and review.
This specification builds upon previous work by Christian Grothoff, This specification builds upon previous work by Christian Grothoff,
Matthias Wachs, Hellekin O. Wolf, Jacob Appelbaum, and Leif Ryge to Matthias Wachs, Hellekin O. Wolf, Jacob Appelbaum, and Leif Ryge to
register .onion in conjunction with other, similar Special-Use Top- register .onion in conjunction with other, similar Special-Use Top-
Level Domain Names. Level Domain Names.
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